The British Guiana Museum. 235 
With this are shewn some most lovely specimens of the 
sea-ears or ear-shells (Haliotis)^ resplendent with beauti- 
ful and changing hues. In these one-valved shells, the 
spiral is much reduced and nearly absent. A valve of an 
English scallop shell, on which two very distinct types 
of life are visible, is also exhibited in this case. In one 
type, belonging to the group of the Molluscs, the animals, 
which are always very minute, form small colonies which 
incrust stones, shells and other objects, sometimes even 
forming branched masses. On the scallop valve, many 
of these little incrusting patches are to be seen, and they 
have been outlined in ink to make them more visible. Each 
patch consists of little egg-shaped or pitcher-shaped 
cells, or shells, all joined together, and during life each 
was occupied by the minute animal that formed it. Though 
so minute, these forms of life are highly organised, being 
true Molluscs of the class Polyzoa — the name given in 
reference to their living in colonies. Often, on the same 
object, numerous groups of colonies may be found, each 
of which may be totally different from the others in 
structure, as much so as the different shells of other forms 
from each other. 
The other type of life represented on the shell is seen in 
the form of little brown sprigs or upright growths. These 
also consist of colonies of little cells — pitchers or tubes ; but 
the animals that form them are of very humble structure, 
being indeed like the little Hydra or fresh-water polype, 
that was described in connection with the blood-corals. 
Unlike the Hydra, they bud repeatedly to form branched 
masses like trees, on which the little beings or 
zooids appear as flowers, so that to the ancient naturalists 
these forms of life were marine plants, and even nowadays 
